Method of making a biosensor

ABSTRACT

The present invention relates to a method of forming a biosensor. The method includes providing a substrate coated with a electrically conductive material, ablating the electrically conductive material to form electrodes and a code pattern, wherein there is sufficient contrast between the conductive coating and the substrate such that the code pattern is discernible, and applying a reagent to at least one of the electrodes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/942,515, filed 29 Aug. 2001, now U.S. Pat. No. 6,814,844.

FIELD OF THE INVENTION

The present invention relates to a biosensor, more particularly to anelectrochemical biosensor with a code pattern thereon.

BACKGROUND AND SUMMARY OF THE INVENTION

Electrochemical biosensors are known. They have been used to determinethe concentration of various analytes from biological samples,particularly from blood. Electrochemical biosensors are described inU.S. Pat. Nos. 5,413,690; 5,762,770; 5,798,031; and 5,997,817 thedisclosure of each of which is expressly incorporated herein byreference. It is also known to include a code on a test strip thatidentifies the manufacturing batch of the strip. See WO 99/22236.

According to one aspect of the present invention a biosensor isprovided. The biosensor comprises a support substrate, an electricallyconductive coating positioned on the support substrate, the coatingbeing formed to define electrodes and a code pattern, wherein there issufficient contrast between the conductive coating and the substratesuch that the code pattern is discernible, and at least one reagentpositioned on at least one electrode.

According to another aspect of the present invention a biosensor isprovided. The biosensor comprises a support substrate, an electricallyconductive coating positioned on the support substrate, the coatingbeing formed to define electrodes and a code pattern, wherein there issufficient contrast between the conductive coating and the substratesuch that the code pattern is discernible, and a cover cooperating withthe support substrate to define a channel. At least a portion of theelectrodes are positioned in the channel.

In addition, a method of forming a biosensor is provided in accordancewith the present invention. The method comprises the steps of providinga substrate coated with a electrically conductive material, ablating theelectrically conductive material to form electrodes and a code pattern,wherein there is sufficient contrast between the conductive coating andthe substrate such that the code pattern is discernible, and applying areagent to at least one of the electrodes.

Still further, in accordance with the present invention a biosensor isprovided. The biosensor comprises a support substrate and anelectrically conductive coating positioned on the support substrate. Thecoating is formed to define electrodes and means for identifying thebiosensor, wherein there is sufficient contrast between the conductivecoating and the substrate such that the identifying means isdiscernible.

Additional features of the invention will become apparent to thoseskilled in the art upon consideration of the following detaileddescription of the preferred embodiment exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a perspective view of a biosensor in accordance with thepresent invention, showing the biosensor formed to include a codepattern formed thereon.

FIG. 2 is an exploded assembly view of the biosensor of FIG. 1, showingthe biosensor including an electrode array positioned at one end, aspacer substrate including a notch, and a cover formed to extend over aportion of the notch.

FIG. 3 is a view taken along lines 3-3 of FIG. 1.

FIG. 4 is a view taken along lines 4-4 of FIG. 1.

FIG. 5 is an enlarged top view of an alternative code pattern formed ona biosensor in accordance with the present invention.

FIG. 6 is an enlarged top view of an alternative code pattern formed ona biosensor in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a biosensor and a method formanufacturing a biosensor that has a specific code pattern. This codepattern is beneficially formed from the same electrically conductivematerial and in the same manner as the electrodes of the biosensor,which reduces steps in the manufacturing process. Laser ablation ispreferably used in forming the code pattern while generating theelectrode pattern. The code pattern can be read in a number of ways,non-limiting examples of which include optically or electricallydepending on the structures formed onto the biosensor. The structurescould show contrast in their optical reflectivity, their electricalconductivity, or their resistance respectively. The structures couldalso be high reflectivity areas surrounded by low reflectivity areas orvice versa, or areas of high electrical conductivity surrounded by areasof low conductivity. Aspects of the invention are presented in FIGS.1-6, which are not drawn to scale and wherein like components in theseveral views are numbered alike.

FIGS. 1-4 illustrate an aspect of the invention in the form of abiosensor 10 having an electrode-support substrate 12, an electricalconductor 13 positioned on the substrate 12 that is disrupted to defineelectrodes 14, 16, a spacer substrate 18 positioned on substrate 12, anda cover substrate 20 positioned on the spacer substrate 18. Biosensor 10is preferably rectangular in shape. It is appreciated however, thatbiosensor 10 can assume any number of shapes in accordance with thisdisclosure. Biosensor 10 is preferably produced from rolls of materialhowever, it is understood that biosensor 10 can be constructed fromindividual sheets in accordance with this disclosure. Thus, theselection of materials for the construction of biosensor 10 necessitatesthe use of materials that are sufficiently flexible for roll processing,but which are still rigid enough to give a useful stiffness to finishedbiosensor 10.

Referring to FIG. 4, the support substrate 12 includes a first surface22 facing the spacer substrate 18 and a second surface 24. In addition,as shown in FIG. 2, substrate 12 has opposite first and second ends 26,28 and opposite edges 30, 32 extending between the first and second ends26, 28. Substrate 12 is generally rectangular in shape, it isappreciated however, that support may be formed in a variety of shapesand sizes in accordance with this disclosure. Substrate 12 is formed ofa flexible polymer and preferably from a flexible polymer and preferablyfrom a polymer such as a polyester or polyimide, polyethylenenaphthalate (PEN). A non-limiting example of a suitable PEN is 5 mil(125 um) thick KALADEX®, a PEN film commercially available from E.I.DuPont de Nemours, Wilmington, Del., which is coated with gold by ROWOCoating, Henbolzhelm, Germany.

Electrodes 14, 16 are created or isolated from conductor 13 on firstsurface 22 of substrate 12. Non-limiting examples of a suitableelectrical conductor 13 include aluminum, carbon (such as graphite),cobalt, copper, gallium, gold, indium, iridium, iron, lead, magnesium,mercury (as an amalgam), nickel, niobium, osmium, palladium, platinum,rhenium, rhodium, selenium, silicon (such as highly dopedpolycrystalline silicon), silver, tantalum, tin, titanium, tungsten,uranium, vanadium, zinc, zirconium, mixtures thereof, and alloys,oxides, or metallic compounds of these elements. Preferably, electricalconductor 13 is selected from the following materials: gold, platinum,palladium, iridium, or alloys of these metals, since such noble metalsand their alloys are unreactive in biological systems. Most preferably,electrical conductor 13 is gold.

Electrodes 14, 16 are isolated from the rest of the electrical conductor13 by laser ablation. See FIG. 4. Techniques for forming electrodes on asurface using laser ablation are known. See, for example, U.S. patentapplication Ser. No. 09/411,940, filed Oct. 4, 1999, now U.S. Pat. No.6,662,439 and entitled “LASER DEFINED FEATURES FOR PATTERNED LAMINATESAND ELECTRODE”, the disclosure of which is expressly incorporated hereinby reference. Preferably, electrodes 14, 16 are created by removing theelectrical conductor 13 from an area extending around the electrodes toform a gap of exposed support substrate 12. Therefore, electrodes 14, 16are isolated from the rest of the electrically-conductive material onsubstrate 12 by a gap having a width of about 25 μm to about 500 μm,preferably the gap has a width of about 100 μm to about 200 μm.Alternatively, it is appreciated that electrodes 14, 16 may be createdby laser ablation alone on substrate 12. It is appreciated that whilelaser ablation is the preferred method for forming electrodes 14, 16given its precision and sensitivity, other techniques such aslamination, screen-printing, or photolithography may be used inaccordance with this disclosure.

As shown in FIG. 2, electrodes 14, 16 cooperate with one another todefine an electrode array 36. In addition, electrodes 14, 16 eachinclude a contact 34 and a lead 38 extending between the contact 34 andthe array 36. It is appreciated that the leads 38 extending from thearray can be formed to have many lengths and extend to a variety oflocations on the electrode-support substrate 12. It is appreciated thatthe configuration of the electrode array, the number of electrodes, aswell as the spacing between the electrodes may vary in accordance withthis disclosure and that a greater than one array may be formed as willbe appreciated by one of skill in the art.

Referring again to FIGS. 2 and 3, a recess 35 is formed from theelectrical conductor 13 by laser ablation using techniques as describedabove. Recess is created by removing the electrical conductor 13 toexpose the first surface 22 of the support substrate 12 adjacent to thefirst end 26. It is appreciated that a portion of the first surface 22may also be removed to form the recess 35 in accordance with thisdisclosure.

In addition, as shown in FIGS. 1, 2, and 4, the discernible code pattern40 is formed from the electrical conductor 13 by laser ablation usingtechniques as described above with reference to electrodes 14, 16.Specifically, the code pattern 40 is created by removing the electricalconductor 13 in a pre-defined pattern to expose the first surface 22 ofthe support substrate 12. While pattern 40 is illustratively a barcodetype pattern, it is appreciated that the pattern 40 can take on anynumber of shapes and patterns, non-limiting examples of which are shownin FIGS. 5 and 6.

It is also appreciated that the pattern 40 can be provided in a humanreadable, optical readable, or electrical readable form in accordancewith this disclosure. The structures could show contrast in theiroptical reflectivity, their electrical conductivity, or theirresistivity respectively. To aid in contrasting the electricalconductivity of the code pattern 40, the electrical conductor 13 of thepattern 40 may be coated with a second conductive material (not shown)that is different from the electrical conductor 13. Non-limitingexamples of the second conductive material include carbon and silver. Itis appreciated, however, that a wide variety of materials may be coatedon the electrical conductor 13 to change the electrical property of thecode pattern 40.

It is also appreciated; electrodes 14, 16 could be formed from layers ofelectrically conductive materials having different colors, reflectivity,conductance, etc. Thus, the code pattern can be formed by removing aportion of the electrical conductor layers, leaving behind areas of highreflectivity surrounded by low reflectivity areas or vice versa, areasof high electrical conductivity surrounded by areas of low conductivityor vise versa. It is also possible to laser etch a code pattern that hasa known resistance and this area can be read electrochemically toidentify or recognize the code pattern. Moreover, it is appreciated thatthe code pattern can be a combination of any of the above readable formsin accordance with the present invention.

As shown in FIG. 4, the code pattern 40 is isolated from the rest of theelectrically conductive material 13 on substrate 12 by gaps 42. Gaps 42can have a wide variety of widths in accordance with this disclosuredepending upon the specific use of the code pattern 40. Non-limitingexamples of widths of the gaps include from about 1 μm to about 1000 μm.Alternatively, it is appreciated that the code pattern 40 may be createdby laser ablation alone on substrate 12. It is appreciated that whilelaser ablation is the preferred method for forming the code pattern 40given its precision and sensitivity, other techniques such aslamination, screen-printing, or photolithography may be used inaccordance with this disclosure.

The manufacturer of biosensor 10 may maintain a central databasecontaining a set of code patterns, each of which uniquely identifies anindividual biosensor, or batch of biosensors. There may also beassociated with each code pattern a set of calibration data for thebiosensor 10. It is appreciated that the code patterns may be associatedwith any number of identification or data sets in accordance with thepresent invention.

Spacer substrate 18 of biosensor 10 includes an upper surface 44 and alower surface 46 facing the substrate 12. In addition, the spacersubstrate 18 includes opposite first and second ends 48, 50. First end48 includes a notch 52, which is defined by a border 54. The borderillustratively includes three generally linear sides. It is appreciatedthat the notch can take on a variety of shapes and sizes in accordancewith this disclosure. When biosensor 10 is assembled, the border 54extends about at least a portion of the array 36 so that the array 36 isat least partially exposed in the notch 52.

Spacer substrate 18 is formed of a flexible polymer and preferably froma flexible polymer and preferably from a polymer such as an adhesivecoated polyethylene terephthalate (PET) polyester. A non-limitingexample of a suitable PET is 3 mil (75 um) thick white PET film bothsides of which are coated with a pressure-sensitive adhesive (Product#ARcare 8877) commercially available from Adhesives Research, Inc. GlenRock, Pa. It is appreciated that spacer substrate 18 may be constructedof a variety of materials and may be coupled to the substrate 12 and thecover substrate 20 using a wide variety of commercially availableadhesives, or by welding (heat or ultrasonic) when large portions of thesurface 22 of the electrode support substrate 12 are exposed and notcovered by electrical conductor 13.

The cover substrate 20 is coupled to the upper surface 44 of the spacersubstrate 18. See FIG. 3. The cover substrate 20 includes opposite firstand second ends 56, 58. The cover substrate 20 is coupled to the spacersubstrate 18 such that the first end 56 is spaced-apart from the end 48of the spacer substrate 18 and the second end 58 is spaced-apart fromthe end 50 of the spacer substrate 18. When biosensor 10 is assembled,cover substrate 20 cooperates with the spacer support 20 and theelectrode-support 12 to define a capillary channel 60.

Cover substrate 20 is generally rectangular in shape, it is appreciated,however, that the cover substrate may be formed in a variety of shapesand sizes in accordance with this disclosure. Cover substrate 20 isformed from a flexible polymer and preferably from a polymer such aspolyester. A non-limiting example of a suitable polymer is 3.9 mil (99um) thick 3M hydrophilic polyester film (3M Product #9971), commerciallyavailable from 3M Healthcare, St. Paul, Minn.

Referring now to FIGS. 1 and 3, the capillary channel 60 is generallylinear in shape and is defined by the cover substrate 20, the electrodesupport substrate 12, and the border 54 of the spacer substrate 18. Whenbiosensor 10 is assembled, channel 60 extends across the electrode array36. Cover substrate 20 does not extend across the entire notch 52,therefore, a portion of the notch serves as an air outlet in accordancewith this disclosure.

An electrochemical reagent 62 is positioned on the array 36. The reagent62 provides electrochemical probes for specific analytes. The termanalyte, as used herein, refers to the molecule or compound to bequantitatively determined. Non-limiting examples of analytes includecarbohydrates, proteins, such as hormones and other secreted proteins,enzymes, and cell surface proteins; glycoproteins; peptides; smallmolecules; polysaccharides; antibodies (including monoclonal orpolyclonal Ab); nucleic acids; drugs; toxins; viruses of virusparticles; portions of a cell wall; and other compounds processingepitopes. The analyte of interest is preferably glucose.

The choice of the specific reagent 62 depends on the specific analyte oranalytes to be measured, and are well known to those of ordinary skillin the art. An example of a reagent that may be used in biosensor 10 ofthe present invention is a reagent for measuring glucose from a wholeblood sample. A non-limiting example of a reagent for measurement ofglucose in a human blood sample contains 62.2 mg polyethylene oxide(mean molecular weight of 100-900 kilo Daltons), 3.3 mg NATROSOL 244M,41.5 mg AVICEL RC-591 F, 89.4 mg monobasic potassium phosphate, 157.9 mgdibasic potassium phosphate, 437.3 mg potassium ferricyanide, 46.0 mgsodium succinate, 148.0 mg trehalose, 2.6 mg TRITON X-100 surfactant,and 2,000 to 9,000 units of enzyme activity per gram of reagent. Theenzyme is prepared as an enzyme solution from 12.5 mg coenzyme PQQ and1.21 million units of the apoenzyme of quinoprotein glucosedehydrogenase. This reagent is further described in U.S. Pat. No.5,997,817, the disclosure of which is expressly incorporated herein byreference.

Non-limiting examples of enzymes and mediators that may be used inmeasuring particular analytes in biosensor 10 are listed below in Table1.

TABLE 1 Mediator (Oxidized Additional Analyte Enzymes Form) MediatorGlucose Glucose Ferricyanide Dehydrogenase and Diaphorase GlucoseGlucose- Ferricyanide Dehydrogenase (Quinoprotein) CholesterolCholesterol Ferricyanide 2,6-Dimethyl-1,4- Esterase and BenzoquinoneCholesterol 2,5-Dichloro-1,4- Oxidase Benzoquinone or PhenazineEthosulfate HDL Cholesterol Ferricyanide 2,6-Dimethyl-1,4- CholesterolEsterase Benzoquinone and Cholesterol 2,5-Dichloro-1,4- OxidaseBenzoquinone or Phenazine Ethosulfate Triglycerides LipoproteinFerricyanide or Phenazine Lipase, Phenazine Methosulfate GlycerolEthosulfate Kinase, and Glycerol-3- Phosphate Oxidase Lactate LactateFerricyanide 2,6-Dichloro-1,4- Oxidase Benzoquinone Lactate LactateFerricyanide Dehydrogenase Phenazine and Diaphorase Ethosulfate, orPhenazine Methosulfate Lactate Diaphorase Ferricyanide PhenazineDehydrogenase Ethosulfate, or Phenazine Methosulfate Pyruvate PyruvateOxidase Ferricyanide Alcohol Alcohol Oxidase Phenylenedia- BilirubinBilirubin Oxidase mine 1- Methoxy- Phenazine Methosulfate Uric AcidUricase Ferricyanide

In some of the examples shown in Table 1, at least one additional enzymeis used as a reaction catalyst. Also, some of the examples shown inTable 1 may utilize an additional mediator, which facilitates electrontransfer to the oxidized form of the mediator. The additional mediatormay be provided to the reagent in lesser amount than the oxidized formof the mediator. While the above assays are described, it iscontemplated that current, charge, impedance, conductance, potential, orother electrochemically indicated property of the sample might beaccurately correlated to the concentration of the analyte in the samplewith biosensor 10 in accordance with this disclosure.

A plurality of biosensors 10 are typically packaged in a vial, usuallywith a stopper formed to seal the vial. It is appreciated, however, thatbiosensors 10 may be packaged individually, or biosensors can be foldedupon one another, rolled in a coil, stacked in a cassette magazine, orpacked in blister packaging.

Biosensor 10 is used in conjunction with the following:

1. a power source in electrical connection with contacts 34 and capableof supplying an electrical potential difference between electrodes 14,16 sufficient to cause diffusion limited electro-oxidation of thereduced form of the mediator at the surface of the working electrode;and

2. a meter in electrical connection with contacts 34 and capable ofmeasuring the diffusion limited current produced by oxidation of thereduced form of the mediator with the above-stated electrical potentialdifference is applied.

The meter is provided with a pattern reader that is capable of readingthe code pattern 40 into a memory of the meter. The reader can be anelectrical or optical reader in accordance with the present invention.The reader is formed to read the code pattern 40 when the bisoensor 10is inserted into the meter. When, however, the code pattern is in ahuman readable form, it is appreciated that the meter may include aninterface, which permits the user to input the information from the codepattern manually. There are many ways to optically read code pattern 40such as laser scanners, pen-like wands, and charge-couple-device (CCD)scanners. A non-limiting example of a suitable optical reader suitablefor use with the present invention includes a light emitting diode(s)(LED), a lens, and a photodiode. It is appreciated that the reader maybe an independent internal component of the meter.

The meter may further be formed to transfer the code pattern from themeter to a memory unit where it is stored. It is appreciated that thememory unit can be formed to store information regarding the specificsof the code pattern as well as patient information including previousmeter readings. The meter will normally be adapted to apply an algorithmto the current measurement, whereby an analyte concentration is providedand visually displayed. Improvements in such power source, meter, andbiosensor system are the subject of commonly assigned U.S. Pat. No.4,963,814, issued Oct. 16, 1990; U.S. Pat. No. 4,999,632, issued Mar.12, 1991; U.S. Pat. No. 4,999,582, issued Mar. 12, 1991; U.S. Pat. No.5,243,516, issued Sep. 7, 1993; U.S. Pat. No. 5,352,351, issued Oct. 4,1994; U.S. Pat. No. 5,366,609, issued Nov. 22, 1994; White et al., U.S.Pat. No. 5,405,511, issued Apr. 11, 1995; and White et al., U.S. Pat.No. 5,438,271, issued Aug. 1, 1995, the disclosures of each of which areexpressly hereby incorporated by reference.

Many fluid samples may be analyzed. For example, human body fluids suchas whole blood, plasma, sera, lymph, bile, urine, semen, cerebrospinalfluid, spinal fluid, lacrimal fluid and stool specimens as well as otherbiological fluids readily apparent to one skilled in the art may bemeasured. Fluid preparations of tissues can also be assayed, along withfoods, fermentation products and environmental substances, whichpotentially contain environmental contaminants. Preferably, whole bloodis assayed with this invention.

To manufacture biosensor 10 a roll of metallized electrode supportmaterial is fed through guide rolls into an ablation/washing and dryingstation. A laser system capable of ablating support 12 is known to thoseof ordinary skill in the art. Non-limiting examples of which includeexcimer lasers, with the pattern of ablation controlled by mirrors,lenses, and masks. A non-limiting example of such a custom fit system isthe LPX-300 or LPX-200 both commercially available from LPKF LaserElectronic GmbH, of Garbsen, Germany.

In the laser ablation station, the metallic layer of the metallized filmis ablated in a pre-determined pattern, to form a ribbon of isolatedelectrode sets on the electrode support material, code patterns, and arecess in the film adjacent to each electrode array. To ablateelectrodes 14, 16, recess 35, and code patterns 40 in 50 nm thick goldconductor 13, 90 mJ/cm² energy is applied. It is appreciated, however,that the amount of energy required may vary from material to material,metal to metal, or thickness to thickness. The ribbon is then passedthrough more guide rolls, with a tension loop and through an optionalinspection system where both optical and electrical inspection can bemade. The system is used for quality control in order to check fordefects.

Upon leaving the laser ablation station, the metallized film is fed intoa reagent dispensing station. Reagents that have been compounded are fedinto a dispensing station where it is applied in a liquid form to thecenter of respective the array 34. Reagent application techniques arewell known to one of ordinary skill in the art as described in U.S. Pat.No. 5,762,770, the disclosure of which is expressly incorporated hereinby reference. It is appreciated that reagents may be applied to thearray 34 in a liquid or other form and dried or semi-dried onto thearray 34 in accordance with this disclosure.

In a separate process, a double-sided pressure-sensitive film with dualrelease liners is fed into a window punch unit where notches are formed.The film is then fed into a lamination & kiss-cutting station. At thesame time, a roll of cover substrate material is fed over a guide rollinto the lamination & kiss-cutting station, where the release liner isremoved from the upper surface 44 and rewound into a roll. The uppersurface 33 of the spacer substrate material is applied to the coversubstrate material. Next, the film is kiss cut and a portion of thecover substrate material is removed, leaving behind the cover substratematerial coupled to the spacer substrate material, extending across aportion of the notch.

The cover material/spacer substrate subassembly is fed into a sensorlamination & cut/pack station. The reagent-coated electrode-supportsubstrate material is fed from the dispensing station into the sensorlamination & cut/pack station as well. The remaining release liner isremoved from the spacer substrate and the spacer substrate is positionedon the electrode-support substrate material so that at least a portionof the electrode array 36 is aligned with the notch 52. Next, theresulting assembled material is cut to form individual biosensors 10,which are sorted and packed into vials, each closed with a stopper, togive packaged biosensor strips.

In use, the meter is turned on and the biosensor is inserted into themeter. It is appreciated that the user may turn on the meter, or it mayturn on automatically upon insertion of the biosensor. The LED emits alight that is directed through a lens towards the code pattern of thebiosensor. The light is reflected off of the code pattern, through thelens, and toward the photodiode. The photodiode measures the intensityof the light that is reflected back from the code pattern and generatesa corresponding voltage waveform. A decoder deciphers this waveform andtranslates it into a reading of the code pattern. It is appreciated thatmany commercially available optical readers may be used in accordancewith the present invention. Preferably, the optical reader will becustom fit reader.

In use, a user of biosensor 10 places a finger having a blood collectionincision against the recess 35 in the notch 52. Capillary forces pull aliquid blood sample flowing from the incision through the capillarychannel 60 across the reagent 62 and the array 34. The liquid bloodsample dissolves the reagent 62 and engages the array 34 where theelectrochemical reaction takes place.

In use for example, after the reaction is complete, a power source(e.g., a battery) applies a potential difference between the electrodes14, 16 respectively. When the potential difference is applied, theamount of oxidized form of the mediator at the reference electrode andthe potential difference must be sufficient to cause diffusion-limitedelectro-oxidation of the reduced form of the mediator at the surface ofthe working electrode. A current measuring meter (not shown) measuresthe diffusion-limited current generated by the oxidation of the reducedform of the mediator at the surface of the working electrode.

The measured current may be accurately correlated to the concentrationof the analyte in sample when the following requirements are satisfied:

1. The rate of oxidation of the reduced form of the mediator is governedby the rate of diffusion of the reduced form of the mediator to thesurface of the working electrode.

2. The current produced is limited by the oxidation of reduced form ofthe mediator at the surface of the working electrode.

The processes and products described above include disposable biosensor10 especially for use in diagnostic devices. Also included, however, areelectrochemical sensors for non-diagnostic uses, such as measuring ananalyte in any biological, environmental, or other sample. As discussedabove, biosensor 10 can be manufactured in a variety of shapes and sizesand be used to perform a variety of assays, non-limiting examples ofwhich include current, charge, impedance conductance, potential or otherelectrochemical indicative property of the sample applied to biosensor.

In accordance with another embodiment of the present invention,biosensor 110 is illustrated in FIG. 5. Biosensor 110 is formed in asimilar manner to biosensor 10 except that biosensor 110 includes a codepattern 140. Code pattern 140 includes nine isolated pads 160. It isappreciated that the number of pads can be greater or fewer than nine inaccordance with this disclosure. Each pad 160 is separated by from thesurrounding electrical conductor by a gap 170.

Code pattern 140 is used once biosensor 110 is attached to a metercircuit board (not shown) that includes a connector. Generally, theconnector will include two contacts per possible pad location onbiosensor 110. Code pattern 140 of the present invention enables themeter to check continuity at each pad 160 location or determine that apad does not exist in a pre-determined location. If a pad 160 ispresent, the meter will recognize the presence of a pad 160 by acontinuity check. One of ordinary skill in the art will be well aware ofmethods suitable for performing a continuity check.

Code pattern 140 is formed from the electrical conductor by laserablation using techniques as described above with reference toelectrodes 14, 16, shown for example in FIG. 1. Specifically, removingthe electrical conductor in a pre-defined pattern to expose the firstsurface of the support substrate 12 creates the code pattern 140. Codepattern 140 can also be coated with a second electrical conductor (notshown) to modify the electrical resistivity of the pattern 140. Whilepattern 140 illustratively includes nine spaced-apart generallysquare-shaped pads, it is appreciated that the pattern 140 can take onany number of shapes and patterns in accordance with this disclosure. Inaddition, it is appreciated that the pattern 140 can be read opticallyor electrically in accordance with this disclosure.

In use, when the user inserts biosensor 110 into the meter (not shown),the biosensor 110 makes contact to the connector and the electronics ofthe meter inquire as to how many pads 160 are showing continuity.Predetermined lot information may be stored in a memory unit of themeter. It is appreciated that the memory unit may also store a varietyof patient information including previous meter readings. This memoryunit is formed with memory components, a non-limiting example of whichis known as RAM, which is well known in the prior art. The results ofthe continuity query may be used to set the appropriate code informationin the meter, which enables the meter to eliminate chemistry or reagentvariation.

In accordance with another embodiment of the present invention,biosensor 210 is illustrated in FIG. 6. Biosensor 210 is formed in asimilar manner to biosensor 10, except that biosensor 210 includes acode pattern 240. Code pattern 240 includes nine pads 260 that are incommunication with one another. It is appreciated that the number ofpads can vary in accordance with this disclosure. Each pad 260 isseparated from the surrounding electrical conductor by gaps 270.

Code pattern 240 is formed from the electrical conductor by laserablation using techniques as described above with reference toelectrodes 14, 16, shown for example in FIG. 1. Specifically, removingthe electrical conductor in a pre-defined pattern to expose the firstsurface of the support substrate 12 creates the code pattern 240. Codepattern 240 can also be coated with a second electrical conductor (notshown) to modify the electrical resistivity of the pattern 240.

While pattern 240 illustratively includes nine generally square-shapedpads that are interconnected, it is appreciated that the pattern 240 cantake on any number of shapes and patterns in accordance with thisdisclosure, which would give various resistance levels. These differingresistance levels can be correlated to a reagent lot. For example, thepattern 240 can be varied by disconnecting the internal links betweenthe pads 260. This disconnection can be done, for example, by a laser.By changing the number of interconnected pads, the resistance of theremaining interconnected pads 260 will be different. In addition, it isappreciated that the pattern 240 can be read optically or electricallyin accordance with this disclosure.

In use, when the user inserts biosensor 210 into the meter (not shown),the biosensor 210 makes contact to the connector and the electronics ofthe meter inquire as to how many pads 260 are showing continuity.Information related to this continuity is similar to that previouslydescribed with reference to biosensor 110.

In addition, the biosensor 210 will make contact with electronics of themeter, which determines the resistance between the interconnected pads.Thus, in preferred embodiments, the meter will determine which padsexist on the biosensor 210, and the resistance of the interconnectedpads 260. The information can be stored in the meter as described abovewith reference to biosensors 10 and 110.

Although the invention has been described in detail with reference to apreferred embodiment, variations and modifications exist within thescope and spirit of the invention, on as described and defined in thefollowing claims.

1. A method of forming a biosensor, the method comprising the steps of:providing a flexible substrate coated with an electrically conductivematerial, ablating through the electrically conductive material toexpose the substrate in a pre-defined pattern so as to form a pattern ofelectrodes and a code pattern electrically isolated from the electrodes,wherein there is sufficient contrast between the conductive material andthe exposed substrate such that the code pattern is discernible, andapplying a reagent to at least one of the electrodes.
 2. The method ofclaim 1 wherein the ablating step includes the step of laser ablatingthe electrically conductive material.
 3. The method of claim 1 whereinthe ablating step includes forming a bar code shaped code pattern. 4.The method of claim 1 wherein the ablating step includes forming a codepattern that includes pads isolated from the surrounding electricallyconductive material.